Dental enamel is a thin, hard layer of calcified material that covers the crown of teeth. The major mineral component of dental enamel is hydroxyapatite, a crystalline form of calcium phosphate. Chemical erosion of dental enamel may arise from tooth exposure to acidic food and drinks or to stomach acids arising from gastric reflux. The erosion of dental enamel can lead to enhanced tooth sensitivity due to increased exposure of the dentin tubules and increased dentin visibility leading to the appearance of more yellow teeth. The salivary pellicle (a thin layer of salivary glycoproteins deposited on teeth) is integral in protecting the teeth against an erosive challenge. As a result, people that experience xerostomia are more susceptible to acid erosion damage.
Existing methods developed to help prevent enamel erosion include incorporating a source of free fluoride into oral care compositions. Fluoride reduces damage to the enamel, through the formation of fluorapatite, which dissolves at a lower pH than hydroxyapatite and so is more resistant to acid damage. Stannous salts have also been incorporated into dentifrice formulations to protect the enamel surface similarly, by forming a more acid resistant mineral layer. Polymers have also been described that coat and protect the enamel surface.
Acids are also generated in the oral cavity when plaque containing cariogenic bacteria metabolize carbohydrates. Since plaque forms a barrier controlling the kinetics of proton and mineral diffusion through the enamel, plaque acids cause carious lesions. Incorporating fluoride ions in dentifrice formulations is the most common method to mitigate the effects of plaque acids. Fluoride reduces the rate of demineralization and enhances remineralization. Several approaches have also been developed to stabilize calcium phosphate salts or control the plaque pH to enhance remineralization.
Although methods have been developed to mitigate the effects of non-bacteria and bacteria generated acids on the teeth, there is still the need to provide improved oral care compositions that effectively repair the enamel from the effects of acid erosion and bacteria acids.